In recent years, to manufacture compact, light electronic appliances for industrial and consumer uses with high quality and high operation frequencies, there is an increasing demand for monolithic ceramic capacitors since they have a large capacitance-to-volume ratio, high mass producibility and superior electrical properties including high frequency characteristics, heat resistance.
Such monolithic ceramic capacitors are generally composed of a dielectric ceramic composition consisting essentially of barium titanates modified with one or more of stannates, zirconates and other titanates. However, the production of the monolithic ceramic capacitors requires use of an expensive noble metal such as Au, Pt and Pd as a material for internal electrodes since the ceramic compositions of the prior arts have a high sintering temperature ranging from 1300.degree. to 1400.degree. C. The use of the noble metal sets a limit to lower the manufacturing cost of the monolithic ceramic capacitors because of a high cost of the noble metal.
To solve this problem, it has been proposed to incorporate a glass component comprising oxides of boron, bismuth and lead into the above modified barium titanate composition. This ceramic composition makes it possible to use a relatively inexpensive silver-paradium alloy as a material for internal electrodes of the monolithic ceramic capacitors since its sintering temperature is relatively low and ranges from 1100.degree. to 1150.degree. C. However, the incorporation of the glass component causes lowering of the dielectric constant, resulting in the increase in size for a given capacitance. Accordingly, it is not possible with such a ceramic composition to lower the manufacturing cost of the monolithic ceramic capacitors.
It is an object of the present invention to provide a dielectric ceramic composition with a low sintering temperature of not more than 1000.degree. C. and a high dielectric constant of not less than 8000.
Another object of the present invention is to provide a dielectric ceramic composition with a high dielectric constant, low dielectric loss, and a low sintering temperature that can be used as a dielectric material for monolithic ceramic capacitors comprising internal electrodes of a relatively inexpensive silverparadium alloy.